Undisclosed Green Synthetics Raise GIA Eyebrows

RAPAPORT... Twenty-five undisclosed lab-grown diamonds have turned up atthe Gemological Institute of America (GIA) - including several with a raregreenish color. The GIA's lab in Carlsbad, California, recently received thestones - weighing from 0.46 to 0.52 carats - for grading reports. They allproved to have been created using High Pressure-High Temperature (HPHT), GIA seniorresearch scientist Sally Eaton-Maga??a explained in a lab note published in theSpring 2019 issue of Gems & Gemology, the institute's quarterlyscientific journal. While nine of the stones were colorless or near-colorless, eighthad faint-yellow-green color, seven were faint green, and one was very lightgreen. The coloring resulted from a high concentration of nickel, an impuritythat's common in HPHT, but rarely in large enough amounts to affect the color, Eaton-Maga??aexplained. (In diamonds at large, nickel can cause a green hue.) GIAgemologists previously reported on a fancy-deep-yellowish-green HPHT diamond in2017, with nickel also the cause in that case. "As laboratory-grown-diamond manufacturers continue toexperiment with their recipes and the process further evolves, we will likelysee greater quantities and a wider variety of color ranges," Eaton-Maga??awrote. The occasion also gave a rare opportunity to analyze a large dataset ofsimilar but unusually colored HPHT diamonds, she noted. The Spring edition of Gems & Gemology alsoreported on a natural diamond with a synthetic layer - the second such case theGIA had seen in about two years. Image: A 0.50-carat, faint-green HPHT synthetic diamond. (Robison McMurtry/GIA)